When many people hear the term "green home," the first image that comes to their minds is one of a sleek, ultramodern home that uses space-age technology to minimize its impact on Earth. Green homes, these people reason, are only effective if they use the absolute latest in modern technology, design and construction.

But some green homes have been here for a while. In fact, many of the so-called "green" design features that modern homebuilders use to improve new homes' efficiency have their roots in very old -- and sometimes ancient -- design and construction techniques.

Human beings have been adapting their homes for efficiency for millennia. Some of the earliest homes, such as those of the ancient Pueblo people of the American Southwest, feature green designs and techniques that were later seen in homes built by famous architects, such as Philip Johnson and Frank Lloyd Wright.

If you're considering building a green home or making green improvements to your existing home, check out this list of historic green homes. Your project may be separated from these structures by hundreds -- or thousands -- of years, but the basic principles that made them efficient could work for your own project.

10

Ardestie Earth House: Scotland

This Iron Age (roughly 1200 to 500 B.C.) structure was likely built with little regard for green building -- at least in the modern sense. The Earth House, located near the city of Dundee, was discovered in early 1949. Over the following year, archaeologists excavated the site, which consists of a series of interlinked huts and underground cellars.

This in and of itself isn't particularly remarkable; archaeologists suggest that this type of construction was common in this location and era [source: Royal Commission on the Ancient and Historical Monuments of Scotland]. From a green building perspective, however, the Ardestie Earth House site offers evidence that our ancestors knew a thing or two about green building even though it would be centuries before the term came into use.

The earth is a very good insulator and building material. Many of the historic green homes on this list make use of earthen walls, or they simply build into the earth rather than on top of it. Not only does this save significant amounts of energy, but it also reduces the amount of material needed to construct standing-room-height interiors. The people who constructed Ardestie Earth House and similar structures in Scotland were likely focused on making the most of the building materials they had and on finding a way to stay as warm as possible during the cold winters. Little did they know that their home incorporated green design features that would be touted by builders centuries later [source: Freed].

9

Peralta Adobe: San Jose, CA, USA

The Peralta Adobe, built in 1797, provides an early example of green construction with good insulation and passive solar heating.

The Peralta Adobe is the oldest home in the California city of San Jose. Historians believe it was built in the late 1700s, and that it's the last standing remnant of El Pueblo de San Jose de Guadalupe, the Spanish settlement that became San Jose [source: Waymarking.com]. Today, the Peralta Adobe is preserved, along with the Victorian-period Fallon House, as living examples of the southwestern city's past [source: History San Jose].

Adobe is a mix of clay and sand that can form extremely long-lasting bricks, walls, floors and other structures. In arid climates, like the deserts of the American Southwest, adobe has been used for centuries as a convenient building material.

Along with that convenience, adobe is an effective option for building energy-efficient structures. Adobe has the ability not only to provide good insulation, but also to retain heat and release it slowly -- think of the steady, even warmth that makes a clay oven such an effective way to cook pizza or bake bread. Passive solar construction, such as placing a greenhouse on the outside of a south-facing adobe wall to provide solar heat to the home, is one of many modern green construction techniques that makes the most of adobe's properties [source: Wilson]. But for the early settlers who built structures like the Peralta Adobe, the material was as much about convenience as energy efficiency.

8

Underground Homes: Coober Pedy, Australia

Dugout and semi-dugout homes, which are completely or partially built underground, have been constructed on every inhabited continent for millennia. The move makes sense, especially in areas with little available building material: what better way to stay warm and dry if timber, thatch and loose stone aren't readily available?

The early underground homes in Coober Pedy, Australia, are a prime example of form following function. Opal miners digging in the region's sandstone would move into their mine shafts after pulling out as much of the gem as they could. Over time, entire communities grew out of the abandoned mines, complete with churches and community gathering spaces. The communities grew even larger as non-miners decided to build their own underground homes, using tunneling machines to create dwellings that surpassed the original hand-dug shafts in their beauty and functionality [source: Outback Australia Travel Guide].

Today, opal mining is no longer practiced in Coober Pedy, but homeowners continue to build and expand underground homes in the stable, insulating sandstone. These are perhaps the most extreme example of a green-building technology -- using the earth itself as walls, roofs and floors -- that has been in use since before recorded history. With the modern homes of Coober Pedy, however, the technique has been refined to an architectural art.

7

Earthships: Taos, NM, USA

You can see both tires and bottles in the construction of this Earthship at the Greater World Earthship Community in Taos, New Mexico.

Architect Michael Reynolds launched the Earthship concept in the late 1960s. After moving to Taos, NM, Reynolds used items like cans, bottles and tires to create organic structures that seemed to grow out of their surroundings. Many Earthships can provide and manage their inhabitants' water, heat, electricity and sewage needs without being connected to outside utilities. These "spaceships on earth" quickly grew in popularity, and Earthship communities, as well as houses sporting Earthship-like features, have been built around the globe [source: Freed].

While most Earthship designs are adapted to the local climate, available materials and user's needs, they often share a number of features. The walls are commonly constructed using old tires packed with dirt, stacked like bricks and covered in an earthen material to make smooth, organically flowing walls. This technique creates walls up to 30 inches (76 centimeters) thick -- a wonderful insulation system that keeps heating and cooling costs extremely low [source: Earthship Biotecture].

Earthships often include passive solar features, such as greenhouses, skylights and windows arranged to make the most of sunlight for light and heating. Using solar arrays, solar heat and geothermal heating, these dwellings can often maintain the desired temperature without outside power.

The Earthship concept extends beyond the home, as well, with organic gardens, composting and rainwater collection. Between the cost savings of this energy efficiency and the low cost of construction, Earthships may provide some of the biggest ecological "bang for the buck" in green homes [source: Earthship Biotecture].

6

The Philip Johnson Glass House: New Canaan, CT, USA

The 1,728-square-foot (160-square-meter) Glass House is noted by architecture historians as one of the first examples of a home fully integrated into the surrounding landscape. The Glass House's greenest feature, from a design standpoint, is its startling transparency: Thanks to four walls of glass, each supported by spare black pillars and framing a glass door, it appears to vanish from view at certain angles [source: The Glass House].

Johnson designed the house in 1947 as part of a "composition" of structures -- it's just one of 14 structures Johnson designed for the 47-acre (19-hectare) site. Most notable among these is Johnson's Brick House, built as a complement to the Glass House. Both structures feature Johnson's signature clean lines and spacious glass walls and windows, which blur the lines between where the interior ends and nature begins [source: Daily Icon].

The Glass House site is a prime example of how environmentally sensitive building doesn't just stop at the solar panels, geothermal systems or high-efficiency windows. Homes that are designed to blend into their natural environments break down the wall between indoors and outdoors, making the home's residents more aware of nature. A home designed in this manner can give its inhabitants a closer connection with the seasons, a better appreciation for natural beauty and a greater awareness of the valuable role nature plays in turning a house into a home.

5

Fallingwater: Mill Run, PA, USA

Frank Lloyd Wright designed Fallingwater, which was completed in 1939 and sits over a waterfall in Pennsylvania.

In the late 1930s, Pittsburgh department-store owner Edgar Kaufmann, Sr., commissioned noted architect Frank Lloyd Wright to build a weekend retreat on the family's property, located along Bear Run in Pennsylvania's Laurel Highlands. The result was Fallingwater, a home that many consider a foundational example of marrying a home with its natural surroundings.

One of Fallingwater's most prominent features is its placement: The house is cantilevered over a cascade of waterfalls. In his notes, Wright states that he wished the family to "live with the falls," rather than simply seeing them from a distant window [source: Western Pennsylvania Conservancy]. From some angles, the house appears to be a natural outgrowth of the rock formations along Bear Run. It juts slightly above the surrounding trees like a rock promontory and spreads naturally along the path carved over eons by the waterfall.

Fallingwater was a luxurious custom vacation home designed for a powerful, wealthy family. But its design influenced a generation of architects and homebuilders. The Case Study Houses of the post-World War II era incorporated the open structure and spacious windows that architects like Wright and Johnson pioneered. While primarily a design concern, these features were forerunners of the passive solar design found in Earthships and other modern green homes. The architectural art that's made Fallingwater a landmark building carries on, as much for its energy-conscious potential as for its sheer beauty [source: Western Pennsylvania Conservancy].

4

Monticello: Charlottesville, VA, USA

Thomas Jefferson can truly be considered one of history's most notable Renaissance men. Monticello, his estate on the edge of the Blue Ridge Mountains in Virginia, reflects the man who built it. The historic home has a number of features that would be common additions in many modern green homes.

The most apparent green features of Monticello have to do with light. The mansion's first-floor rooms feature skylights that channel light through from the upper story. Ample glass doors throughout the home reflect a combination of Roman and French architectural influences, but also serve to help keep the house temperate and well lit throughout the seasons [source: Monticello]. In essence, Jefferson designed a passive-solar heat and light system long before the term came into use.

Small details of the estate, though not traditionally green, also speak to the environmental awareness that went into Monticello's design. A weather vane atop the front porch can be read in any weather, thanks to a remote dial. A clock in the main hall uses gravitational pull to track the hours and days in a manner that anyone can read [source: Monticello]. One can argue that modern green homes that connect the occupants to the natural world owe at least some of their inspiration to Jefferson's clever estate.

3

Kasubi Tombs: Kampala City, Uganda

Mutesa I, king of Buganda from 1856 to 1884, was buried in this thatched tomb near Kampala, Uganda, shown here in 1906.

Thatch -- tightly bundled, overlapping layers of grass, reeds or similar vegetation -- is a time-tested green building material. Cultures throughout the world developed variations of thatched roofs and walls, all of which adapted to the varying climates to accomplish the same goal: keeping inhabitants warm and dry.

Thatch can be created from fast-growing, easily replenished plants, making it a truly renewable building material. It's also an excellent insulator. Many houses with thatch roofs use a simple framework to support the thatch; roofs properly built from this material can fulfill the insulation requirements that several layers of shingles, sub-roofing and roof material do in a modern roof [source: McGhee & Co. Roof Thatchers].

One of the largest and most historic thatch roofs in the world is part of the Kasubi Tombs, near Kampala City in Uganda. Four kings of Buganda are buried within a main tomb at this World Heritage Site. A towering forest of poles supports the giant roof, which shelters not only the tombs but also a one-of-a-kind collection of historic relics. Unfortunately, in March 2010, a fire swept through the main tomb, destroying many of these relics.

The legacy of this massive thatch structure can be seen across the globe. Modern homes -- and rehabbed historic homes -- are being rebuilt with thatch roofs, which can last for 60 years when properly constructed [source: McGhee & Co. Roof Thatchers]. And thanks to modern fire-retardant technology, the chance of fire destroying these green roofs is significantly reduced.

2

America's Oldest Net-zero House: Ann Arbor, MI, USA

The historic green buildings listed so far have one thing in common: They were originally built with features that -- intentionally or not -- reduced their effect on their surroundings, saved energy or used resources in an efficient manner. This home in Ann Arbor's Old West Side neighborhood is green through a different tactic: Its current owners turned the rehabilitation of a typical 110-year-old home into an exercise in low-impact living.

The home is considered net zero because it produces as much energy as it consumes. Thanks to a solar array installed on the roof, a geothermal heat system and an energy-recovery ventilator, the home's owners can power modern, energy-efficient lighting and appliances without depending on power from the electric grid. In fact, the owners report that their home produces excess energy, which is then sold back to the power company. In the future, this could be a case of a home providing enough energy to keep its occupants warm, cook their food and power an electric car [source: GreenovationTV].

The house's owners documented the rehabilitation project online, showing energy-conscious homebuyers two important things: First, buying and owning a green home doesn't mean giving up the historic charm of a house with a history. Second, energy efficiency can be part of the plan for any dwelling, regardless of its age. After all, if a drafty Victorian home can become net zero, there's no reason a newer home can't do the same.

1

Cliff Dwellings: Mesa Verde National Park, CO, USA

The cliff dwellings at Mesa Verde National Park in Colorado were some of the earliest green homes.

Few images of the American Southwest are as iconic or familiar as those of the cliff dwellings at Mesa Verde National Park in Colorado. During the period from roughly 600 to 1300 A.D., the Pueblo people lived in this city that was literally built beneath the arch of a large, overhanging cliff. Inhabitants of the city's 600 structures used a series of balconies and ladders to reach their homes, and they were protected from intruders by the natural fortress around them [source: National Park Service].

Mesa Verde is perhaps the most dramatic example of a design feature found in many of the historic green structures on the list. It follows a philosophy of working with the natural surroundings rather than against them. The Pueblo people used the materials at hand: rough-hewn stone from the arid desert. While this is a practice as ancient as the first human-constructed dwellings, it takes on a green meaning when one considers the transportation costs that go into moving and using modern construction materials.

The Pueblo people took advantage of a natural feature that would protect them from wind, rain and snow without major construction efforts. Modern green construction may lean heavily on technology such as active solar power, geothermal heat and high-efficiency appliances, but as the breathtaking structures at Mesa Verde show, green building can be as much about logic and practicality as the latest high technology.

To learn more about green building, check out the links on the next page.

Gettleman, Jeffrey and Josh Kron. "Suspicion of Arson at Royal Tombs Fuels Deadly Clashes in Uganda." The New York Times. March 17, 2010. (Feb. 5, 2011)http://www.nytimes.com/2010/03/18/world/africa/18uganda.html